The present invention relates to a rotary electric machine including a stator having a coil and a cooling unit that cools a coil end of the coil, which projects in an axial direction of the stator.
A rotary electric machine is used conventionally in various devices as a driving power supply. A large output is often required of this type of rotary electric machine, and therefore a large amount of heat is generated from various parts of the rotary electric machine, in particular a coil and a permanent magnet. The causes of this heat generation from the rotary electric machine include copper loss and iron loss. Copper loss occurs invariably when a current is caused to flow into the coil, regardless of the magnitude of the current, and increases in proportion to the square of the current flowing into the coil. Iron loss, meanwhile, is constituted by hysteresis loss and eddy current loss, and occurs when a magnetic material is located within an alternating field. Hysteresis loss occurs when a magnetic field orientation of a magnetic domain of an iron core is varied by the alternating field, and eddy current loss is caused by an eddy current generated during magnetic flux variation in a conductor. These losses are emitted in the form of thermal energy, in other words, Joule heat, leading to heat generation in the coil and the permanent magnet of the rotary electric machine.
When this heat generation becomes excessive, dielectric breakdown may occur in the coil, or more specifically in an insulation varnish insulating lead wires of the coil from each other or insulating paper insulating phase coils from each other. Therefore, a rotary electric machine may be provided with a cooling device capable of appropriately cooling a coil provided in the rotary electric machine. A cooling device that cools an electric motor serving as a rotary electric machine provided in a power transmission apparatus for a vehicle (Japanese Patent Application Publication No. JP-A-2007-312569, for example) is known as an example of this type of cooling device.
The cooling device described in Japanese Patent Application Publication No. JP-A-2007-312569 includes an annular oil pipe that cools an annular coil end that projects in an axial direction from, and forms a circumferential continuation of, an end surface of a stator provided in an electric motor, and the oil pipe forms a circumferential continuation of the coil end. The annular oil pipe is constituted by an outer peripheral annular oil pipe disposed on an outer peripheral side of the coil end so as to overlap the coil end in the axial direction, and an inner peripheral annular oil pipe disposed on an inner peripheral side of the coil end so as to overlap the coil end in the axial direction. A plurality of discharge holes though which cooling oil is discharged toward the coil end are formed in the outer peripheral annular oil pipe and the inner peripheral annular oil pipe. By supplying the cooling oil to the outer peripheral side and the inner peripheral side of the coil end from the plurality of discharge holes, the coil end is cooled.